It is a mistake to think that instrumental rationality fixes a single standard for judging or describing actions. While there is a core conception of instrumental rationality, we appeal to different elaborations of that conception for different purposes. An action can be instrumentally rational in some sense(s) but not in others. As we learn more about behavior, it is possible to add useful elaborations of the core conception of instrumental rationality. In this paper, I propose a newelaboration based on Frederic Schick’s work on understandings